 \begin{tikzpicture}[
node distance = 2cm and 2cm,
     N/.style = {circle, draw, font=\Large, 
                 minimum size=1.1em},
       every edge/.style = {draw, -Stealth, semithick, shorten >=2pt},
every edge quotes/.style = {auto=right, inner sep=2pt}
                        ]
\node (m) at (0,0) {\uppercase\expandafter{\romannumeral1}第一条通路:FA1};
\node[N] (a) at ([xshift=4em,yshift=0em]m.east)[label=left :{+ -}] {1};
\node[N] (b)[right of=a] {2};
\node[N] (c)[right of=b][label=right :{-}]{3};
\node[N] (d)[below of=b][label=right :{-}]{4};

\node (n) at ([xshift=0em,yshift=-2em]m.south){+ $\circledtext{1}   \stackrel{\mathbf{a}}{\longrightarrow}\circledtext{2}\stackrel{\mathbf{c}}{\longrightarrow}\circledtext{3}_{-}$};
\node (p) at ([xshift=2em,yshift=-2em]n.south){+ $\circledtext{1}   \stackrel{\mathbf{a}}{\longrightarrow}\circledtext{2}\stackrel{\mathbf{b}}{\longrightarrow}\circledtext{2}\stackrel{\mathbf{c}}{\longrightarrow}\circledtext{3}_{-}$};
\node (q) at ([xshift=2em,yshift=-2em]p.south){+ $\circledtext{1}\stackrel{\mathbf{a}}{\longrightarrow}\circledtext{2}\stackrel{\mathbf{b}}{\longrightarrow}\circledtext{2}\stackrel{\mathbf{b}}{\longrightarrow}\circledtext{2}\stackrel{\mathbf{c}}{\longrightarrow}\circledtext{3}_{-}$};
\node (v) at ([xshift=-3em,yshift=-2em]q.south) {\uppercase\expandafter{\romannumeral2}第二条通路:FA2};
\node (s) at ([xshift=0em,yshift=1em]v.north){...};
\node (n1) at ([xshift=0em,yshift=-2em]v.south){+ $\circledtext{1}   \stackrel{\mathbf{\varepsilon }}{\longrightarrow}\circledtext{1}_{-}$};
\node (p1) at ([xshift=0em,yshift=-2em]n1.south){+ $\circledtext{1}   \stackrel{\mathbf{b}}{\longrightarrow}\circledtext{4}_{-}$};
\node (q1) at ([xshift=2em,yshift=-2em]p1.south){+ $\circledtext{1}   \stackrel{\mathbf{b}}{\longrightarrow}\circledtext{4}\stackrel{\mathbf{b}}{\longrightarrow}\circledtext{4}_{-}$};
\node(c1)[draw,rectangle callout,callout relative pointer={(-1,1)},rounded corners,align=center] at ([xshift=14em,yshift=-6em]a.west) {接受空串的\\FA的典型特征!};
\node (v1) at ([xshift=14em,yshift=0em]n1.east){$\therefore$ $\rm{L(F A 1)=\left\{a b^{n} c \mid n \geqslant 0\right\}}$};
\node (d1) at ([xshift=0em,yshift=-2em]v1.south){$\therefore$ $\rm{L(F A 2)=\left\{b^{n} \mid n \geqslant 0\right\}}$};
\node (v1_1) at ([xshift=0em,yshift=-2em]d1.south){$\therefore$ $\rm{L(F A)=\left\{a b^{n} c \mid n \geqslant 0\right\}}$};
\node (l) at ([xshift=0em,yshift=-1em]q1.south) {...};
\draw[red, -{Triangle[width = 18pt, length = 8pt]}, line width = 10pt] ([xshift=2em,yshift=0em]q.south) -- ([xshift=0em,yshift=0em]v1.west);
\draw[red, -{Triangle[width = 18pt, length = 8pt]}, line width = 10pt] ([xshift=0em,yshift=0em]q1.east) -- ([xshift=0em,yshift=0em]d1.west);
\path
(a) edge [above] node {a} (b)
    edge [above] node {b} (d)
(b) edge [above] node {c} (c)
    edge [loop above] node {b} ()
(d) edge [loop above] node {b} ()
    ;
    \end{tikzpicture}